Many refrigerator cabinet designs cause certain surface regions of the cabinet to exhibit a tendency to be chilled below the dew point of the ambient air, such that condensate or "sweat" forms on these surfaces. One such region is located about the door sealing gasket. This condensate is unsightly and may have a deleterious effect on surface finish and wet the floor areas below these regions and, accordingly, it is sought to be avoided in most refrigerator designs.
If these regions are heated so as to be warmed above the dew point temperature of the ambient air, the formation of such condensate is avoided.
One approach which is currently widely practiced is the use of electric heating cables disposed within the refrigerator cabinet panels which are turned on and off as needed to prevent the condensate formation. While this is relatively simple to incorporate and readily controllable by a manual control switch, electric heating is relatively inefficient and increases the power required to operate the appliance.
The refrigerator system includes structure which is at a relatively elevated temperature, i.e., the compressor and the condenser coil. This relatively warm structure thus represents a possible heat source whenever the compressor is running which does not require an extra energy source. Rather, heat may be utilized which is otherwise merely dissipated into the surrounding room air.
Accordingly, it has heretofore been proposed to utilize a heat transfer system for utilizing this heat source to heat those regions of the refrigerator cabinet which are subject to the formation of condensate. Several examples of such systems are found in U.S. Pat. Nos. 2,141,918; 2,444,667; 2,537,314; and 2,651,187.
These systems typically incorporate a so-called "secondary loop" refrigerant circulation system in which a loop of tubing containing fluid material which can act as a refrigerant is placed in contact with relatively warm portions of the refrigerator structure such as the compressor housing or the condenser loop.
The relatively warm temperature heats the refrigerant within the secondary loop causing it to be vaporized and passed into the upper regions of the loop, which are located at the cabinetry regions to be warmed.
The resultant cooling of the heated refrigerant causes the refrigerant to condense releasing heat to warm the cabinet, the liquid refrigerant flowing back to the warm region in liquid form. Repetition of the cycle allows a relatively effective heat transfer means for utilizing the heat source provided by the warm or hot components of the refrigeration equipment and accordingly does not require any additional power in order to generate the anti-sweat heat.
The warming of the cabinet regions of course represents a thermal load on the refrigeration system. That is, the heat conducted into the interior space of the refrigerator is increased since the secondary loop is often located at regions where insulation is at a minimum causing the refrigeration equipment to be operated longer in order to maintain the refrigerated space at the desired temperature. Thus, this system does inherently create an energy loss which is required in the power to operate the appliance, and if this approach is taken to avoid exterior condensate, some inefficiency is unavoidable.
However, at times, the use of such an anti-sweat system is not required since the dew point of the ambient air may be sufficiently low that the existing temperature of the exterior surfaces will not result in the formation of condensate. This may occur at certain times of the year in certain locales, i.e., during the winter heating season, the extremely dry air within the building will reduce the dew point to the point where cabinet warming is not required. Similarly, in desert climes, the system may never be necessary. While such appliances are generally manufactured to a design adapted to all climates encountered within the market area, the unnecessary heat load could be avoided if the system were not operated.
Heretofore, such secondary loop systems have not been controllable and have been inherently permanently in operation by virtue of their design.
In U.S. Pat. No. 2,651,187, the system is mounted so as to heat the peripheral edges of the access door and in this patent, the heat transfer path is interrupted upon the door being opened. However, no separately operable control member is utilized which could be used to discontinue operation of the secondary loop when the need for cabinet warming is not required. The aforementioned electric cable heating systems generally provide a manually operable switch which allows selective operation of the cabinet heating to conserve power, but heretofore no heating system has been provided for secondary loop or heat transfer type cabinet warming devices.
The specific arrangement disclosed in the listed patents for heating the secondary loop is relatively cumbersome in that it requires relatively permanent affixation to the compressor motor, or portions of the refrigerator frame. This adds to the cost of manufacture.
It is accordingly an object of the present invention to provide a heat transfer cabinet warming device for refrigerator cabinetry in which the cabinet warming process is selectively controllable.
It is another object of the present invention to provide such a device in which a very simple arrangement for the transfer of heat from the heat source is manually controllable by a control member which is manipulated manually to interrupt the transfer of heat into the cabinet areas.
It is still another object of the present invention to provide an arrangement for producing heating of a secondary loop section by an easily installed arrangement and which allows thermal contact to be interrupted.